Isometric torgue-angle relationship of the elbow flexors and axtensors in the transverse plane
- I. J. Pinter, F. Robbert M, J. Knoek van Soest A, B. J. Smeets J
- Journal of Electromyography and Kinesiology
The aim of this study was to investigate the influence of the joint position on elbow flexors and extensors torque in healthy individuals and to compare the modeling of peak torque-angle relationships with polynomial functions and cubic splines. Fifteen male volunteers (between 19 and 24 years) were measured anthropometric parameters and peak, isometric-torque with isokinetic dynamometer at the following angles: 10, 20, 30, 45, 60, 75, 90, 105, 115 and 125o. It was found that the maximumal peak-torque (Nm) is generated at 75o in flexors and extensors at significant increase (p <0.05, one way ANOVA, Bonferoni post hoc test) in angular positions between 45o and 75o as compared with the rest angles tested. The torque of the flexors was greater than that of the extensors (p <0.05) in the area of the flexion, within the range of 90o-115o. The maximal isometric force decreased in a narrow range and never fell below 60% with the extensors and 70% with the flexors at any of the tested angles. It was established a moderate correlation (r>0.5, coefficient of Pearson) in both muscle groups between: height and peak torque (at 30° and 45° for extensors and 115o for flexors); and muscle mass and torque (at 45° for extensors and 105°, 115o and 125o for flexors). It was only with the flexors, that moderate to significant correlations were observed between peak torque and body mass (105° and 115o), lean body mass (105°, 115o and 125o) and body mass index (105°). The modeling of peak torque-angular position relationship with polynomials of fourth degree was considered optimal, according to the two criteria applied, only for extensors. With the flexors the assessment by the two criteria was ambiguous. The approximative curves in modeling with polynomials did not cover all points, including the maximum peak torque, which is not the global maximum of the optimal function. However this was achieved by interpolating cubic spline curves. It was found in the present study, that the peak, isometrictorque of the elbow flexors and extensors in healthy males: (1) is maximal at the angular position of 75o and is not reduced by more than 30% with the flexors and 40% with the extensors, at any of the tested positions; (2) correlates with anthropometric parameters, which is most manifested for the height and muscle mass in both muscle groups; and (3) is preferable to be modeled with cubic splines, compared to polynomial functions. The specifics of the torque profile as a function of the angular position is determined by the initial length of the muscles and their synergic contribution to the net torque.